The theory of coupling oscillators is always attractive, but the implementation thereof is thwarted by problems of instability.
EP Patent 2365403 in the name of SEAGULL discloses an oscillator for a mechanical timepiece comprising a first balance freely rotating about an axis; and a balance spring connecting this first balance to a fixed point or to a second balance, the balance spring comprising: a first coil connected to the first balance and a second coil connected to the fixed point or to the second balance, and a transition section connecting the first coil to the second coil, wherein a substantially linear restoring torque for at least one balance is essentially ensured by the elastic deformation of the transition section and the coils to produce an oscillating motion for at least one balance.
CH Patent 709281 in the name of THE SWATCH GROUP RESEARCH & DEVELOPMENT describes a forced oscillation resonator arranged to oscillate at a natural frequency and comprising, on the one hand, at least one oscillating member, and on the other hand, means for maintaining oscillation arranged to exert a torque on the oscillating member, which carries at least one oscillating regulator device whose natural frequency is a regulation frequency that is comprised between 0.9 times and 1.1 times an integer multiple of the natural frequency of said resonator mechanism, the integer being greater than or equal to 2. In particular, the regulator device includes, mounted to pivot freely on the oscillating member, at least one secondary sprung balance with an eccentric unbalance with respect to the secondary pivot axis about which the secondary sprung balance pivots.
EP Patent 112633 in the name of SEIKO describes a mechanical timepiece comprising a mainspring powering the mechanical time source, and a rotational angle control mechanism formed such that, in a state where the spring is completely wound, the air resistance is applied to rotation of the balance returned by a balance spring, and, in a state where the spring is completely unwound, the air resistance is not applied to rotation of the balance with the balance spring.
CH Patent 699081 in the name of THE SWATCH GROUP RESEARCH & DEVELOPMENT describes a resonator resulting from the coupling of a first low frequency resonator with a second higher frequency resonator, wherein the first resonator includes a first inertial mass associated with a first spring, the second resonator includes a second inertial mass associated with a second spring, and wherein a third spring is disposed between the first and second inertial masses for coupling the first and second resonators.
WO Patent 2016/037717 in the name of ETA MANUFACTURE HORLOGERE SUISSE discloses a regulator comprising, mounted to move in at least a pivoting motion with respect to a plate, an escape wheel arranged to receive a drive torque via a gear train, a first oscillator comprising a first rigid structure connected to the plate by first elastic return means. This regulator also comprises a second oscillator with a second rigid structure connected to the first rigid structure by second elastic return means, which are arranged to allow at least a pivoting motion of the second rigid structure with respect to the first rigid structure. The second structure comprises guide means arranged to cooperate with complementary guide means comprised in the escape wheel, together forming a motion transmission means for synchronizing the first oscillator and the second oscillator with the gear train.